yego.me
💡 Stop wasting time. Read Youtube instead of watch. Download Chrome Extension

Fields | Forces at a distance | Middle school physics | Khan Academy


3m read
·Nov 10, 2024

  • If you hold a ball up in the air and let it go, you know it's going to fall, but why? Nothing is touching it once you let it go. How can there be a force on it? Well, this is because Earth's gravitational force is pulling the ball, and gravity is a non-contact force. Non-contact forces don't have to touch an object to exert a force on it. Instead, these forces act over a region.

So if an object is in that region, it will be affected by the force. In this case, the ball is in Earth's gravitational field, and so it feels an attractive force towards the Earth, and the ball falls to the ground. Field forces include non-contact forces, such as electric, magnetic, and of course, gravitational forces. So since these forces are non-contact, they can exert a force on objects they aren't touching, but how do these objects know if there's a force between them?

To explain these non-contact forces, scientists eventually developed the idea that these objects were surrounded by something called a field. So what is a field? A field extends through space from an object with certain physical properties. What are those? Well, for gravitational forces, these affect objects with mass. So any object with mass has a gravitational field surrounding it that points towards the object's center.

The further you move away from the object, the less dense the field, and weaker the field becomes. Electric forces affect charged objects. So an electric field surrounds any object with a net charge, and the direction of this field will depend on the charge. Magnetic fields will affect magnets and any other material with magnetic properties.

Each spot on a field has two things associated with it: magnitude and direction. And these help us predict what forces objects will experience when they're in the field. So let's look at an example to help understand this. Say we have a planet. Now, the planet has a lot of mass, so we know it's going to be surrounded by a gravitational field that points towards the center of the planet.

I can draw these little field lines that show the direction of the field and its strength. As we move away from the planet, the field will start to weaken, and I'm going to represent that by a less dense field with these arrows. Now, let's say there's an asteroid moving near the planet in this direction. I know that the asteroid, as it's shown here, is in the outskirts of this planet's gravitational field.

So it is going to feel some gravitational attraction towards the planet, which we can draw with this vector, Fg, which is the force of gravity. Now, because it's attracted to the planet, the asteroid will continue to move towards the planet. And the closer the asteroid gets to the planet, the stronger the field and the stronger the force of attraction it will feel.

And so in this way, scientists can use fields to help predict the behavior of objects experiencing non-contact forces. And all of this may sound kind of odd, but you probably already think about forces this way. For example, if we go back to the ball that you know is going to fall, you knew this because the force of gravity from Earth was going to pull the ball towards the Earth.

But now you also know that that's because Earth's gravity is a field force. And so the ball is in the field of gravity for Earth and experiences an attractive gravitational force. So while fields may sound mysterious, they really just mean that a force is felt over a distance. Gravitational, electric, and magnetic forces are all field forces, which means they act over distance and can affect a lot of objects.

More Articles

View All
The Most Radioactive Places on Earth
[Music] So I’m not B H. It’s overloaded; radiation is frightening, at least certain types of it are. I mean, my Geiger counter doesn’t go off near my mobile phone or the Wi-Fi router or my microwave. That’s because a Geiger counter only measures ionizing …
5 Things To Know Before Buying An ETF | Stock Market for Beginners
Hey guys and welcome back to the channel! So if you’re watching this video, you are interested in ETFs, and that is awesome! Maybe you’re making a first-time investment, and if that’s you, welcome to the world of investing! Get pumped up because it is a g…
Pope Francis: The Story Behind National Geographic's Cover Photo | Nat Geo Live
[Music] Dave: What was tougher, covering the pope for six months or slogging through a Honduran jungle looking for a lost city? Oh well, it was definitely much harder to access the Vatican than the jungle. For me, when you work around the pope, you have…
BITCOIN TO $500,000 - What You MUST Know
What’s up, Graham? It’s guys here, and I’m not gonna lie, sometimes it feels like we’re living in the golden era of the finance and investment community. Although I realize that “golden era” might not be the proper term here because we’re not talking abou…
Charlie Munger's Final Call on Alibaba Stock.
Charlie Munger, despite being 98 years old, is without doubt one of the smartest minds that lives today. From a young man who simply dreamed of financial independence, he’s now worked alongside Warren Buffett to not only become a multi-billionaire but als…
Force vs. time graphs | Impacts and linear momentum | Physics | Khan Academy
There’s a miniature rocket ship, and it’s full of tiny aliens that just got done investigating a new moon with lunar pools and all kinds of organic new life forms. But they’re done investigating, so they’re going to blast off and take their findings home …